This invention relates to voltage regulation.
An integrated circuit chip, such as a microprocessor, often requires multiple supply voltages for different parts of the chip circuit. This may reduce power consumption of components that can utilize a lower voltage than the other portions of the chip. A main supply voltage may be provided to the chip from an off-chip source, and an on-chip power converter may be used to generate additional supply voltages from the main supply voltage. When the main supply voltage from an off-chip source is the highest of the supply voltages used in the chip, a xe2x80x9cseries voltage regulatorxe2x80x9d may be used to obtain the other supply voltages that are lower than the main supply voltage.
FIG. 1 shows a conceptual model of a series voltage regulator 10 that includes a controllable series resistor R1 connected between a main power supply (with voltage VIN) and an output node 12 (with voltage VOUT). For a constant load current ILOAD, the value of R1 may be constant. If the load changes over time, a feedback circuit that includes a differential amplifier 14 connected to a reference voltage VREF may be used to dynamically adjust the value of R1 in order to keep the output voltage VOUT substantially constant. The reference voltage VREF may be generated by using a band-gap reference circuit that produces a constant voltage independent of operating temperature and processing conditions. A second resistor R2 may be connected between output node 12 and ground 13 to achieve better control of the output voltage VOUT. In a CMOS process, resistors R1 and R2 may be implemented using MOSFET devices.